I prefer fiction because it is not constrained by what has happened. Nonfiction is firmly in the realms of reality. With fiction the story can go anywhere. It can have ludicrous plot twists. Completely unorthodox characters. It can use plot elements that are impossible to us but are absolutely vital to the story at hand. To me the idea of a poet traveling through the 9 circles of Hell is far more interesting than anything that could possibly happen in the real world. I am of course mentioning the Divine Comedy. Not to say that nonfiction cant be exciting. All I'm saying is fiction has the potential to be more exciting.